Numerical simulations of odorant detection by biologically inspired sensor arrays

Abstract

The antennules of many marine crustaceans enable them to rapidly locate sources of odorant in turbulent environmental flows and may provide biological inspiration for engineered plume sampling systems. A substantial gap in knowledge concerns how the physical interaction between a sensing device and the chemical filaments forming a turbulent plume affects odorant detection and filters the information content of the plume. We modeled biological arrays of chemosensory hairs as infinite arrays of odorant flux-detecting cylinders and simulated the fluid flow around and odorant flux into the hair-like sensors as they intercepted a single odorant filament. As array geometry and sampling kinematics were varied, we quantified distortion of the flux time series relative to the spatial shape of the original odorant filament as well as flux metrics that may be important to both organisms and engineered systems attempting to measure plume structure and/or identify chemical composition. The most important predictor of signal distortion is the ratio of sensor diameter to odorant filament width. Achieving high peak properties (e.g. sharpness) of the flux time series and maximizing the total number of odorant molecules detected appear to be mutually exclusive design goals. Sensor arrays inspired specifically by the spiny lobster Panulirus argus and mantis shrimp Gonodactylaceus falcatus introduce little signal distortion but these species' neural systems may not be able to resolve plume structure at the level of individual filaments via temporal properties of the odorant flux. Current chemical sensors are similarly constrained. Our results suggest either that the spatial distribution of flux across the aesthetasc array is utilized by P. argus and G. falcatus, or that such high spatiotemporal resolution is unnecessary for effective plume tracking.

Peer Review #1 of "Scaling of olfactory antennae of the terrestrial hermit crabs Coenobita rugosus and Coenobita perlatus during ontogeny (v0.1)"

“…Since odor molecules cannot be delivered to the surface of the aesthetascs by fluid currents alone due to the entrained fluid layer, molecular diffusion must transport molecules across the boundary layer (Stacey et al, 2002;Schuech et al, 2012). Molecular diffusion is molecular movement by a random walk causes a change in concentration over time.…”

A tale of two antennules: the performance of crab odour-capture organs in air and water

“…During the return stroke, the arrays trap water between the hairs [15]. This sequence creates a flow-no flow pattern within the aesthetasc array, allowing marine crabs to take discrete samples of odour-containing water [7,16,17]. The ability to discretely sample is an important aspect of odour capture [18].…”

“…We present a novel approach to studying odour capture in different fluid habitats using a computational model of odour capture. Previously, odour capture by aesthetascs has been simulated by coupling flow and diffusion near the hairs of a single species [16,17,23]. In each case, the flow fields were either taken from measurements on dynamically scaled models or from numerical simulations of a single fluid environment.…”

Scaling of olfactory antennae of the terrestrial hermit crabs Coenobita rugosus and Coenobita perlatus during ontogeny

“…Since odor molecules cannot be delivered to the surface of the aesthetascs by fluid currents alone due to the entrained fluid layer, diffusion must transport molecules across the boundary layer (Stacey et al, 2002;Schuech et al, 2012). Diffusion is molecular movement by a random walk which causes a change in concentration over time.…”